Top 7 Science-Backed Benefits of Ashwagandha Capsules

Ashwagandha has been a cornerstone of Ayurvedic medicine for centuries, known for its ability to boost strength, vitality, and mental clarity.

Yet modern medicine remained skeptical of its benefits—until recently.

New research is now confirming many of ashwagandha’s traditional uses. Studies show that ashwagandha capsules can reduce anxiety, improve sleep, enhance athletic performance, and support immune health.

And that’s why ashwagandha has become a go-to supplement for anyone looking to optimize their mind, body, and overall well-being.

In this article, you’ll discover what ashwagandha is, how it works, and the top science-backed benefits of adding it to your supplement regimen.

What Is Ashwagandha?

Ashwagandha is a root from Ayurveda, the traditional Indian system of medicine. It comes from the ashwagandha plant, also known as Withania somnifera, which grows in India, Africa, and the Middle East.

It’s often called “the horse herb” because the name “ashwagandha” means “smell of horse,” a nod to its strong odor. People used to say it gave you the strength of a horse, too—an early example of marketing hype.

The key thing to know about ashwagandha is that it’s an adaptogen—a substance that helps you “adapt” to stress. It works by causing a small, unperceivable stress in the body, which triggers a stronger response to handle future stressors more effectively.

Traditionally, men used ashwagandha to boost vitality, vigor, sexual well-being, and strength. Today, it’s a popular supplement for enhancing cognitive function, mood, athletic performance, and overall health.

What Is KSM-66 Ashwagandha Extract?

Spend any time researching ashwagandha capsules, and it won’t be long until you hear mention of “KSM 66 ashwagandha extract.” 

But what exactly is KSM-66, and how does it differ from regular ashwagandha?

KSM-66 ashwagandha is a patented form of ashwagandha found in many top-quality supplements. It contains 5% withanolides, the active compounds that provide most of ashwagandha’s benefits. 

All ashwagandha supplements contain some withanolides, but their concentration can vary from 1% to over 35%, depending on how manufacturers grow, process, and store the plant. Supplements that don’t specify withanolide content might contain too little to be effective or too much to be safe.

The source of withanolides also matters. 

KSM-66 ashwagandha uses only the root of the ashwagandha plant, while some manufacturers use the leaves to cut costs. While there’s no direct evidence that leaf-based supplements are harmful, most studies focus on the root, not the leaves.

That’s why many consider KSM-66 the gold standard of ashwagandha extracts, especially when it comes to supplements. 

What Does Ashwagandha Do?

As I’ve mentioned, ashwagandha’s benefits come primarily from a group of molecules called withanolides.

There are more than a dozen withanolides, but the two most important are withanolide A and withaferin A. These are the most potent and abundant in ashwagandha.

At this point, I’d usually dive into how these molecules interact with the body—but here’s the catch: we still don’t fully understand how adaptogens, like ashwagandha, work in the brain.

And then there’s withaferin A—a “promiscuous” molecule. 

In chemistry, promiscuity refers to molecules that interact with many different “targets,” and withaferin A is a prime example. This makes research tricky because it’s hard to pinpoint exactly what it’s doing.

Still, scientists have made some educated guesses about how ashwagandha works.

A leading theory is that it influences the hypothalamic-pituitary-adrenal (HPA) axis—the system that controls how your body responds to stress, which could explain its wide-reaching effects.

That said, there’s still much we don’t know. Ashwagandha may affect the HPA axis differently in different people, which might explain why studies sometimes show mixed results.

The Top 7 Ashwagandha Benefits

Research shows that KSM-66 ashwagandha provides the following seven benefits:

1. Increased power, strength, and endurance
2. Reduced stress and anxiety
3. Lower cortisol
4. Enhanced sleep quality
5. Reduced inflammation and higher antioxidant levels
6. Improved fertility in men
7. Better immune function

Let’s look at each in more depth.

Increased Power, Strength, and Endurance

Research shows that taking ashwagandha boosts strength and power output in weightlifters and sedentary folks alike.

For example, in a study published in the journal Nutrients, weightlifters taking ashwagandha gained significantly more strength than those taking a placebo.

Those taking ashwagandha capsules increased their bench press strength by 101 pounds versus 58 pounds in the placebo group, and their leg extension strength by 32 pounds compared to 22 pounds.

They also gained more muscle, lost more fat, had higher testosterone levels, and experienced less muscle damage.

It also appears to enhance cardiovascular endurance, particularly VO2 max.

Reduced Stress and Anxiety

Studies show that ashwagandha helps reduce anxiety caused by chronic stress.

In one study, people with chronic stress reported feeling much less anxious after taking ashwagandha. Another study found it helped reduce stress-related overeating in obese people, which helped them lose weight.

Ashwagandha also appears to be effective for tackling general anxiety, though the effects are strongest when stress is the main cause.

Interestingly, ashwagandha may even improve “social functioning.”

Studies on rats show increased social interaction, and some human studies report “improved sociability” (willingness to participate in social activities) as a side benefit, even when stress isn’t the root issue.

Lowered Cortisol

Cortisol is a hormone that spikes in response to stress. While it’s helpful for increasing alertness, fat burning, and reducing inflammation in the short term, consistently elevated cortisol can cause the opposite—leading to fatigue, fat gain, disease, and dysfunction.

Studies show that taking ashwagandha capsules can reduce cortisol levels by 15-to-28% in stressed individuals. In animal studies, this reduction has led to better immune function, as cortisol can suppress the immune system.

What’s impressive here is the magnitude of the effect. 

In a world full of exaggerated supplement claims, a 15% reduction in cortisol is a meaningful result, making ashwagandha one of the more potent options for managing stress-induced cortisol spikes.

Enhanced Sleep Quality

Research shows that ashwagandha can significantly improve sleep quality, even for people with insomnia.

In one 8-week study, 80 participants split into 4 groups: those without sleep issues and those with insomnia, with each group further split into ashwagandha or placebo groups.

The researchers gave those taking ashwagandha 600 mg daily (300 mg twice a day), and then tracked everyone’s “sleep onset latency” (how long it took to fall asleep), total sleep time, and mental alertness upon waking at 1, 4, and 8 weeks.

The results were impressive.

Those taking ashwagandha capsules, especially those with insomnia, fell asleep faster, slept longer, and reported better sleep quality and higher alertness in the morning compared to the placebo groups.

Another 6-week study involving 150 healthy adults with sleep disturbances reported similar findings. Participants who took 120 mg of ashwagandha extract experienced significant improvements in sleep onset, total sleep time, sleep efficiency, and reduced waking during the night. 

What’s more, self-reported sleep quality increased by 72% in the ashwagandha group, compared to just 29% in the placebo group, and their overall quality of life also improved.

Reduced Inflammation and Increases Antioxidant Levels

Results from studies on memory impairment show that taking ashwagandha capsules reduces inflammation in the brain and protects brain cells from oxidative damage. 

This effect is linked to withaferin A and withanone, which help repair neurons and improve connections between them.   

Ashwagandha also helps balance the levels of important proteins in your brain, like brain-derived neurotrophic factor (BDNF) and glial fibrillary acidic protein (GFAP), which are crucial for brain health and memory.

Improved Fertility in Men

For generations, men have used ashwagandha to boost fertility.

Today, research supports this traditional use, showing that ashwagandha can improve sperm quality, regulate key fertility hormones, and protect the reproductive system from damage.

It also helps alleviate stress and anxiety, which are major contributors to sexual dysfunction.

For instance, a 2022 study involving 50 healthy men showed that ashwagandha root extract improved overall sexual function, including sexual desire, arousal, and performance.

Men taking ashwagandha capsules were also 89% more likely to improve their overall sexual health compared to the placebo group, with significant improvements in areas like arousal, behavior, orgasm, and desire.

Enhanced Immune Function

Ashwagandha appears to support immune health, though it’s unclear if this is due to its ability to reduce stress, which can weaken your immune defenses.

In other words, it may indirectly boost immune function by lowering stress rather than directly improving how your immune system works.

Still, studies show taking ashwagandha capsules can improve several markers of immune function and may also play a role in preventing or treating respiratory infections.

Ashwagandha’s antioxidant and anti-inflammatory properties may explain some of its immune benefits. 

For instance, research shows that taking 500-to-5,000 mg daily for 8-to-12 weeks can increase antioxidants, reduce oxidative stress markers like malondialdehyde, and improve exercise recovery, lung function, and overall quality of life.

Does Ashwagandha Increase Testosterone?

A common claim is that ashwagandha benefits testosterone production, boosting “T” in even the most virile men.

While this probably isn’t true, there’s evidence that it can increase T in some scenarios

For instance, ashwagandha has been shown to raise testosterone levels in men with fertility issues, particularly when their infertility is related to stress or poor semen quality. 

This effect may be due to ashwagandha’s antioxidant properties, which help protect the testicles and improve hormone production. 

The only study on ashwagandha and testosterone in otherwise healthy men comes from research on new weightlifters. 

In this study, ashwagandha capsules improved muscle mass and strength, and testosterone levels increased by around 15%.

Crucially, this boost in testosterone may have been a side effect of gaining muscle rather than the cause of it. After all, getting stronger and more muscular can naturally raise testosterone in newbie weightlifters.

Unfortunately, there’s not enough evidence to say whether ashwagandha boosts testosterone in healthy, fertile, active men. 

Interestingly, ashwagandha may also enhance libido, but this may not be related to testosterone levels. For example, studies on women have shown improvements in sexual function without any changes in testosterone.

So, while taking ashwagandha capsules may technically increase testosterone, this effect is likely more relevant to men with fertility issues or those dealing with stress-induced hormonal imbalances. In healthy men, its role may be more as a testicular antioxidant than a testosterone booster.

What Is the Clinically Effective Ashwagandha Dosage?

According to most studies, the most effective dose of ashwagandha is 500-to-600 mg daily. While it’s not essential, taking it with a meal is generally recommended.

What Are the Most Common Side Effects of Ashwagandha?

Ashwagandha is generally safe, though can cause side effects on rare occasions.

These side effects vary—some people report unexpected benefits like improved appetite or libido, while others experience reactions like vertigo. 

Likewise, many users find it helps with sleep, but a few have reported the opposite effect.

One potential issue involves its impact on thyroid function. Ashwagandha increases thyroid hormones (T3 and T4), which may help people with subclinical hypothyroidism. However, the effect can be unpredictable, and there’s at least one case of excess thyrotoxicosis (excess thyroid hormones) linked to its use.

For this reason, people with overactive thyroids or those on thyroid medication should avoid ashwagandha.

What’s the Best Ashwagandha Supplement?

If you want to supplement with ashwagandha, you should buy it from a trusted source.

That’s because it’s common for herbal supplements to be underdosed (they don’t contain as much of the active ingredients as they say on the label), and some can be contaminated with toxins like arsenic, mercury, lead, and cadmium.

If you’re looking for a safe source of ashwagandha, check out Legion’s KSM-66® ashwagandha root extract.

Third-party labs test our KSM-66® ashwagandha for heavy metals, microbes, allergens, and other contaminants to ensure it meets strict purity standards.

It also contains 600 mg of KSM-66 ashwagandha per serving, which is the amount shown by scientific research to enhance cognitive function, mood, and athletic performance and reduce inflammation and oxidative stress.

(Or, if you aren’t sure if Legion KSM-66® ashwagandha root extract is right for you or if another supplement might better fit your budget, circumstances, and goals, then take the Legion Supplement Finder Quiz! In less than a minute, it’ll tell you exactly what supplements are right for you. Click here to check it out.)

FAQ #1: What are ashwagandha’s benefits for athletes?

Ashwagandha offers a range of benefits for athletes, especially when it comes to enhancing cognition, reaction time, and overall mental sharpness.

One study found that taking 250 mg of ashwagandha twice a day improved reaction time, decision-making, and mental focus in healthy young adults—skills crucial for athletes who need to make fast, accurate choices under pressure.

Ashwagandha also helps stabilize mood and reduce stress, allowing athletes to stay calm and focused during competition. Its ability to lower cortisol can also aid in recovery and improve performance.

Beyond the mental benefits, ashwagandha’s benefits for working out include boosting endurance, strength, and recovery.

FAQ #2: What are the effects of ashwagandha on hair loss?

Many people are curious about whether ashwagandha can help with hair loss. While there’s no solid evidence showing ashwagandha prevents or reverses hair loss, one case study does offer some insight.

Doctors from the New York Department of Internal Medicine found ashwagandha to be effective in treating congenital adrenal hyperplasia, a genetic disorder that can lead to hair loss. While this is just one case study and not enough to draw broad conclusions, it may offer hope for those dealing with this condition.

Beyond that, no substantial evidence links ashwagandha to improved hair health. So, while it’s not a proven solution for hair loss, it could be worth considering if you’re dealing with specific issues like congenital adrenal hyperplasia.

FAQ #3: How long does it take for ashwagandha to work?

Most studies show that regular ashwagandha supplementation improves physical and emotional well-being within 4-to-12 weeks. That said, the exact timeline varies from person to person.